Vertical/horizontal amplitude controller

ABSTRACT

The vertical/horizontal amplitude control device for controlling a vertical amplitude and a horizontal amplitude of an image display device for displaying a video signal includes a brightness level detector for detecting a brightness level of the video signal, a vertical amplitude controller for controlling the vertical amplitude based on the brightness level, and a horizontal amplitude controller for controlling the horizontal amplitude based on the brightness level. The device controls the vertical and horizontal amplitudes into constant without a delay from a change of a video signal even when the brightness level of the video signal abruptly changes.

This application is a National Phase Application Under 35 U.S.C. 371,claiming the benefit of PCT/JP02/11434 filed Nov. 1, 2002, which haspriority based on Application No. 2001-345590 filed in Japan on Nov. 12,2001.

TECHNICAL FIELD

The present invention relates to a vertical/horizontal amplitude controldevice for a cathode-ray tube (CRT) television receiver.

BACKGROUND ART

In association with recent trend toward a larger screen size, a higherpicture quality, and a higher quality, it is important that the picturesize of a cathode-ray tube (CRT) television receiver be unchangeddespite a change of a high voltage. A conventional vertical/horizontalamplitude control device for controlling a change of the picture sizedue to the change of the high voltage will be described.

FIG. 3 is a block diagram of the vertical/horizontal amplitude controldevice for controlling vertical and horizontal amplitudes based on thechange of the high voltage. A video signal is converted into RGB signalsin RGB processor block 31. Amplitudes of the signals are then controlledin gain control block 32, and the video signal is displayed on picturetube 33. A beam current that flows when displaying the video signal isdetected as the change of the high voltage. The change of the highvoltage is supplied to vertical amplitude control section 34 andhorizontal amplitude control section 35. By controlling the verticalamplitude and the horizontal amplitude according to the change of thehigh voltage, a change of the picture size due to the high voltagechange can be reduced. Vertical sawtooth-wave controller 36 controls alinearity of a vertical sawtooth wave and performs an S-characteradjustment. Pin-cushion controller 37 performs a waveform control of apin-cushion waveform.

Since the above sections control vertical and horizontal amplitudesafter a beam current flows, that is, after the high voltage changes, thecontrol device cannot correct the amplitudes appropriately because of adelay of control of the vertical and horizontal amplitudes after thechange of the high voltage. This causes the change of the vertical andhorizontal amplitudes not to be reduced due to the high voltage change.

SUMMARY OF INVENTION

A vertical/horizontal amplitude control device for controlling anvertical amplitude and an horizontal amplitude of an image displaydevice for displaying a video signal includes a brightness leveldetector for detecting a brightness level of a video signal, a verticalamplitude controller for controlling the vertical amplitude based on thebrightness level, and a horizontal amplitude controller for controllingthe horizontal amplitude based on the brightness level. The devicemaintains the vertical and horizontal amplitudes in constant withoutdelay from a change of the video signal even when the brightness levelof the video signal has abruptly changed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a vertical/horizontal amplitude controldevice according to an exemplary embodiment of the present invention.

FIG. 2A is a flowchart of an amplitude control of thevertical/horizontal amplitude control device according to theembodiment.

FIG. 2B is a flowchart of an amplitude control of a conventionalvertical/horizontal amplitude control device.

FIG. 3 is a block diagram of the conventional vertical/horizontalamplitude control device.

FIG. 4A to FIG. 4F illustrate signal waveforms of thevertical/horizontal amplitude control device according to theembodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

FIG. 1 is a block diagram of a vertical/horizontal amplitude controldevice according to an exemplary embodiment of the present invention.RGB processor 1 generates an RGB signal from a video signal input to theprocessor by using a matrix, and performs DC control and amplitudecontrol of the video signal. The RGB signal output from RGB processor 1is transferred through delay line 2 and gain controller 3, and isdisplayed on a video display device, such as cathode-ray tube (CRT) 4.

Delay circuit 2 cancels a time difference between a change of verticaland horizontal amplitudes due to a change of a high voltage and acorrection of the vertical and horizontal amplitudes based on results ofa detection of a brightness level. Delays are caused in amplifiers andfilters, for example, while signals travel from vertical amplitudecontroller 6 and horizontal amplitude controller 7 to a verticaldeflection and a horizontal deflection, respectively. Consequently,delay circuit 2 is provided in a channel of transmission of the videosignal for adjusting a delay time of the RGB signals, so that the timingof correction of the vertical and horizontal amplitudes matches adisplay on the screen of the CRT. Delay circuit 2 may be omitted if notnecessary.

Brightness level detector 5 calculates the brightness level of the RGBsignals output from RGB processor 1, that is, the brightness levelcorresponding to a beam current that is deemed flowing in picture tube3. The brightness level changes depending on an RGB amplitude adjustmentand a black level adjustment. Brightness level detector 5 calculatesrespective average brightness levels in a short time range (e.g. ahorizontal deflection period) and in a long time range (e.g. a verticaldeflection period). The average brightness levels can be calculated, forexample, by adding the brightness level of each pixel and dividing thesum of the brightness levels by the horizontal deflection period andvertical deflection period, respectively. The levels are output as aresult of the detection of the brightness level. That is, the verticaland horizontal amplitudes can be controlled both in the short time rangeand in the long time range. As a result, the vertical and horizontalamplitudes of the screen are controlled in the short time range in analternating-current type signal level change while the amplitudes arecontrolled in the long time range in a direct-current type signal levelchange.

Brightness level detector 5 detects the average brightness level.Alternatively, the detector may detect a peak, a pattern, a maximumvalue, a minimum value, or a green output or any of their combination.The detector may detect an average brightness level only in the shorttime range or an average brightness level only in the long time range.

Vertical amplitude controller 6 for controlling the amplitude of areference sawtooth wave for vertical deflection on a vertical synchsignal as the trigger controls the vertical amplitude substantiallysimultaneously to a flowing of a beam current according to an output ofbrightness level detector 5 that corresponds to beam current flowing inpicture tube 4 in a manner such that the vertical size of a picture doesnot change. Similarly, substantially when a beam current flows,horizontal amplitude controller 7 for controlling the horizontalamplitude controls the horizontal amplitude based on an output ofbrightness level detector 5 according to a beam current flowing inpicture tube 4 in a manner such that the horizontal size of a picturedoes not change. Vertical sawtooth-wave controller 8 controls alinearity of vertical sawtooth-waves and performs an S-charactercorrection, and pin-cushion controller 9 controls a pin-cushion waveformcontrolled by horizontal amplitude controller 7.

An operation of the above-mentioned vertical/horizontal control devicewill be described with reference to FIG. 2A and FIG. 2B. FIG. 2A is aflowchart of high-voltage control of the vertical/horizontal amplitudecontrol device according to the embodiment. FIG. 2B is a flowchart ofhigh-voltage control in a conventional vertical/horizontal amplitudecontrol device. The conventional control device widens vertical andhorizontal amplitudes after a high voltage decreases due to an increaseof the beam current of the picture tube that is caused by an increase inthe brightness level of a signal output. Therefore, the vertical andhorizontal amplitudes are not widened by the time they should be wideneddue to a time loss. That is, the vertical and horizontal amplitudesshould be widened simultaneously to the decreasing of the high voltage.As shown in FIG. 2A, the vertical/horizontal amplitude control device ofthe embodiment detects the brightness level from RGB signals andcontrols the vertical and horizontal amplitudes based on the brightnesslevel. By predicting a decreasing of the high voltage in advance in thisway, the control device of the embodiment prevents the time loss andcontrols the vertical and horizontal amplitudes rapidly. Theconventional control device generates a delay from the decreasing of thehigh voltage to the controlling of the amplitudes. This causes thepicture size to momentarily shrink and then return to a normal size, andhas a viewer feel uncomfortable. The control device of the embodimentdoes not have the viewer feel uncomfortable since not generating thetime loss.

As described above in detail, the vertical/horizontal amplitude controldevice of the embodiment controls the vertical and horizontal amplitudeswithout the delay even when the brightness level of the video signalchanges rapidly.

FIG. 4A to FIG. 4F show signal waveforms of the vertical/horizontalamplitude control device of the embodiment. In FIG. 4A, a solid linerepresents a video signal corresponding to a small brightness level ofthe output of RGB processor 1. A broken line represents a video signalcorresponding to a large brightness level. The larger the brightnesslevel is, the larger a load of high voltage increases, thus causing adecrease of the high voltage. FIG. 4B represents a waveform of the highvoltage. As shown in FIG. 4C, when the high voltage decreases, thevertical and horizontal sizes of a picture decrease. According to thepresent invention, since the brightness level is detected by digitalprocessing, the video signal level can be easily detected andcontrolled, and the video signal level can be easily transmitted tovertical amplitude controller 6 and horizontal amplitude controller 7when the video signal is output to the picture tube. As shown in FIG. 4Dand FIG. 4F, vertical amplitude controller 6 controls the amplitude of avertical sawtooth-wave while horizontal amplitude controller 7 controlsa DC level of a horizontal pin-cushion correction waveform. As shown inFIG. 4F, the controllers control the vertical and horizontal amplitudesbased on the brightness level of the video signal without a time lossand thus maintains a constant picture size independently from thebrightness level.

The number of bits of the signal to be transmitted from the brightnesslevel detector to the vertical and horizontal amplitude controllers isat least ten because of the resolution of the vertical amplitude. If thenumber of bits is small, the change of the vertical amplitude due to thechange of the video signal is visible and provides the viewer with anuncomfortable feeling as a change of a digital nature. According to theinvention, the amplitudes are controlled through the digital processing,however may be similarly controlled through an analog processing. Thevertical and horizontal amplitudes may be controlled in combination witha conventional control device, that is, based on the detected brightnesslevel as well as on the change of the high voltage. Furthermore, thehorizontal amplitude may be controlled through the control of the DClevel of the pin-cushion correction waveform.

INDUSTRIAL APPLICABILITY

The vertical/horizontal amplitude control device of the presentinvention controls vertical and horizontal amplitudes of a video displaydevice, such as a cathode-ray tube (CRT), at a constant level withoutdelay from a change of the video signal even in when a brightness levelof the video signal abruptly changes.

REFERENCE NUMERALS

-   1 RGB Processor-   2 Delay Circuit-   3 Gain Controller-   4 Image Display Device-   5 Brightness Level Detector-   6 Vertical Amplitude Controller-   7 Horizontal Amplitude Controller-   8 Vertical Sawtooth Waveform Controller-   9 Pin-Cushion Controller

1. A vertical/horizontal amplitude control device for controlling avertical amplitude and a horizontal amplitude which change a verticalsize and a horizontal size of an image display device for displaying avideo signal, said vertical/horizontal amplitude control devicecomprising: a brightness level detector for detecting an average of abrightness level of said video signal and a peak of said brightnesslevel in a vertical deflection period, and an average of a brightnesslevel of said video signal and a peak of said brightness level in ahorizontal deflection period; a vertical amplitude controller forcontrolling said vertical amplitude in order to change the vertical sizeof said image display device based on said average of said brightnesslevel of said video signal and said peak of said brightness level insaid vertical deflection period; and a horizontal amplitude controllerfor controlling said horizontal amplitude in order to change thehorizontal size of said image display device based on said average ofsaid brightness level of said video signal and said peak of saidbrightness level in said horizontal deflection period.
 2. Thevertical/horizontal amplitude control device of claim 1, furthercomprising a delay circuit for delaying said video signal supplied tosaid image display device.
 3. The vertical/horizontal amplitude controldevice of claim 2, wherein, when said average of said brightness levelof said video signal and said peak of said brightness level in saidvertical deflection period increases, said vertical amplitude controllerwidens said vertical amplitude, and when said average of said brightnesslevel of said video signal and said peak of said brightness level insaid horizontal deflection period increases, said horizontal amplitudecontroller widens said horizontal amplitude.
 4. The vertical/horizontalamplitude control device of claim 2, wherein said brightness leveldetector detects said brightness level by digital processing.
 5. Thevertical/horizontal amplitude control device of claim 1, wherein saidvertical amplitude controller controls said vertical amplitude bycontrolling an amplitude of a reference sawtooth wave, and saidhorizontal amplitude controller controls said horizontal amplitude basedon said reference sawtooth wave having the amplitude controlled.
 6. Thevertical/horizontal amplitude control device of claim 5, wherein, whensaid average of said brightness level of said video signal and said peakof said brightness level in said vertical deflection period increases,said vertical amplitude controller widens said vertical amplitude, andwhen said average of said brightness level of said video signal and saidpeak of said brightness level in said horizontal deflection periodincreases, said horizontal amplitude controller widens said horizontalamplitude.
 7. The vertical/horizontal amplitude control device of claim5, wherein said brightness level detector detects said brightness levelby digital processing.
 8. The vertical/horizontal amplitude controldevice of claim 1, wherein, when said average of said brightness levelof said video signal and said peak of said brightness level in saidvertical deflection period increases, said vertical amplitude controllerwidens said vertical amplitude, and when said average of said brightnesslevel of said video signal and said peak of said brightness level insaid horizontal deflection period increases, said horizontal amplitudecontroller widens said horizontal amplitude.
 9. The vertical/horizontalamplitude control device of claim 1, wherein said brightness leveldetector detects said brightness level by digital processing.